diff --git a/lib/sql.py b/lib/sql.py
index 1c780902..13548da4 100644
--- a/lib/sql.py
+++ b/lib/sql.py
@@ -442,7 +442,7 @@ class Placeholder(Composable):
 
     def as_string(self, context):
         if self._wrapped is not None:
-            return f"%({self._wrapped})"
+            return f"%({self._wrapped})s"
         else:
             return "%s"